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Discussion Starter · #1 ·
I recently bought a 97 XJ that had overheated I tore into it and did a new head gasket along with everything that hose with it, new head bolts, valve cover gasket intake gasket, I have it back together and runs great but I’m getting cylinder 1 misfire, and can not figure it out, I swapped injectors 1#2 not difference, new plugs wires cap and all, I’ve checked vaccums replaced ccv elbow that was broke not sure were else to go, grounds seem fine
 

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Did you check the head for warpage or cracks? Did you have the block shaved? How many miles were on the engine? Did you do a compression test, before and after?
 

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Discussion Starter · #4 ·
Didn’t have the block shaved, I went Over it for 2 days checking for cracks and had a feeler gauge and I couldn’t find anything, didn’t check compression before I knew from the start it was blown head gasket, checked after and was good, I did the upper motor sea foam treatment, a new air filter and swapped plugs with 1 &2 to see if it was possibly the plug the other day and drove it yesterday for first time since and at one point I got cylinder 1&2 misfire with one code of random misfire, those were new,
 

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Discussion Starter · #5 ·
Did you check the head for warpage or cracks? Did you have the block shaved? How many miles were on the engine? Did you do a compression test, before and after?
The only thing that comes to mind is you might still have a head gasket leak. You can have your coolant tested for exhaust gasses and see how that comes out
I feel like I would overheat after the 300 miles I’ve put in it or have some coolant loss and I don’t and the plug Dosent show signs of leaking
 

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Discussion Starter · #8 ·
Didn’t think so but wasn’t sure, I’ve read in few other forums that fixed the issue for similar problems, What about my muffler? It is full of holes and in bad shape, I’m going to replace it just haven’t got to it yet, could a horrible exhaust leak leak like that cause this issue? The 02s have been replaced along with an own manifold just not the muffler itself
 

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Check to make sure you are getting signal to fuel injector #1 and #2. Wondering if they aren't firing due to bad connection or corroded/broken wiring
 

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Discussion Starter · #11 ·
So about the misfire, I’ve noticed, I can go out and start the jeep and it’s fine, put it in gear and with in 2 mins of driving it throws the PO301 code, I can stop turn it off to clear the code with my computer. I then start it back up and drive any distance/amount of time without it throwing the code again until I shut it off and start it back that’s after any amount of time being off. I have on several occasions left the computer hooked up to watch live data to see if I see anything and sometimes not always it will show PO301 code as pending but not thrown yet and some times it’s not even pending. The misfire isn’t bad at first but after driving for long period of time it gets somewhat worse, throttle response get slightly hesitant,a little jerky feeling setting at a red light, vibrates exhaust very loud and twice I’ve heard the notorious 4.0 knock sound. (only after running for really long period). I was hoping running it might break up some carbon build up that sea-foam top engine cleaner didn’t get and possibly clear up itself. After it’s at temp for 20mins or so you can clearly hear the misfire but again gets worse with time. If I’m throttled up at RPM higher then idle the misfire sounds gone and it sounds amazing and runs absolutely amazing when like in passing gear. Yesterday after a drive I decided to mess with the injector 1&2 while running I moved them around and got not change, I then unplugged them an my computer picked up an open circuit on both injectors but as far as running you would have never knew I in hooked them, I got an amazing deal on this rig and I’ve put money in parts, and a whole lot of labor, I’m almost to the point of posting for sell, I love working on vehicles and learning new stuff but I have exhausted my entire mental book if knowledge, I bought an 99 last week with a leaky trans and good motor with 123,xxx miles I could swap but I had to tear apart a super clean 99 that’s just needs a trans filter and gasket, thanks everybody for the help I hope I covered everybody questions in this
 

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Discussion Starter · #13 ·
Check to make sure you are getting signal to fuel injector #1 and #2. Wondering if they aren't firing due to bad connection or corroded/broken wiring
[/Yesterday after a drive I decided to mess with the injector 1&2 while running I moved them around and got not change, I then unplugged them an my computer picked up an open circuit on both injectors but as far as running you would have never knew I in hooked them,
 

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i have been following a fella on you tube known as scanner danner. he uses an oscilloscope, test light and multimeter to troubleshoot issues. you can see the amount of spark you are getting from your plugs, and be able to see how long a injector is open. you can view your cam and crank signals, looking at these from the inside can help determine what the problem might be. I know alot of people get very frustrated with these issues and want to set it on fire. unfortunately, these problems can be infuriating. it's most likely an electrical issue, but pinpointing it can be mind numbing. I am in PA, where are you located?
 

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Discussion Starter · #15 ·
i have been following a fella on you tube known as scanner danner. he uses an oscilloscope, test light and multimeter to troubleshoot issues. you can see the amount of spark you are getting from your plugs, and be able to see how long a injector is open. you can view your cam and crank signals, looking at these from the inside can help determine what the problem might be. I know alot of people get very frustrated with these issues and want to set it on fire. unfortunately, these problems can be infuriating. it's most likely an electrical issue, but pinpointing it can be mind numbing. I am in PA, where are you located?
Yes can be very aggravating, especially when your able to tear the top end down and rebuild it, but then get stuck on something as small as a misfire, wiring has been in the back of my head for a while I was just hoping to save that for last cause that can be very time consuming and tedious, when I bought the jeep knowing it had gotten pretty hot, I did notice a section of wires that runs out of the Plastic bar beside valve cover has a few spots that’s the outer sleeve has some melting, and the the middle slot of the plastic case itself had melted a good bit, so I was just hoping I missed something else before chase if wires, they can be more elusive than Bigfoot, and from N.C
 

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I recently bought a 97 XJ that had overheated I tore into it and did a new head gasket along with everything that hose with it, new head bolts, valve cover gasket intake gasket, I have it back together and runs great but I’m getting cylinder 1 misfire, and can not figure it out, I swapped injectors 1#2 not difference, new plugs wires cap and all, I’ve checked vaccums replaced ccv elbow that was broke not sure were else to go, grounds seem fine
My wife’s 97 xj developed that same code. I changed the cam position sensor under the distributor rotor because it failed a resistance test. I also changed the crank position sensor with a genuine Mopar replacement. Don’t get the cheap one. Fixed the problem and it’s stayed gone for over 3 years now. Might be worth a check and cheap if it’s bad. Good luck!
 

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the wiring harness that goes around the rear of the valve cover can short out. the harness rubs against one of the valve cover bolts that are also a stud and one of the internal wires shorts out. Only takes a minute to check.
 

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Discussion Starter · #18 ·
Check to make sure you are getting signal to fuel injector #1 and #2. Wondering if they aren't firing due to bad connection or corroded/broken wiring
After a few days or tinkering iam thinking it may be either the injector connector or wiring. I traced down a good portion of the wire and on# 1 there were many portions that looked bad possible broke under the coating, I checked straightened and even cut an shrink tubed back together, an it now it runs great more but still have the misfire in #1 just not as often and not as bad as it had been, it seems with every thing I try it helps small amounts but nothing has completely fixed the misfire, I ordered new injectors and I’m looking into pulling the wires from the connector and investigating if that could be the issue, are one replacement connections sold? Or not worth buying them just fix wire one mine? Not sure it the contact points could just go out completely due to inability to clean them thoroughly due to being so small
 

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Discussion Starter · #19 ·
the wiring harness that goes around the rear of the valve cover can short out. the harness rubs against one of the valve cover bolts that are also a stud and one of the internal wires shorts out. Only takes a minute to check.
I haven’t made it that far back yet in wiring currently going through the bundle that sits in the plastic case that runs along side the valve cover
 
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